Thursday, August 28, 2014

New paper describes another solar amplification mechanism that affects low clouds

A paper published today in Geophysical Research Letters finds another potential solar amplification mechanism by which tiny changes in the solar wind affect clouds and pressure [geopotential height anomalies] in the lower troposphere. 

The authors find this new mechanism to be distinct from previously described solar amplification mechanisms involving 
"downward propagation of atmospheric effects to the lower troposphere from the stratosphere due to solar-variability-driven mechanisms involving ultra-violet radiation or energetic particle precipitation."
The newly described solar-wind-driven amplification mechanism is also distinct from the solar-wind-driven mechanism of Svensmark's cosmic ray theory of climate, and adds to many other potential solar amplification mechanisms described in the scientific literature. 


Solar-wind-driven geopotential height anomalies originate in the Antarctic lower troposphere

Mai Mai Lam et al


We use NCEP/NCAR reanalysis data to estimate the altitude and timelag dependence of the correlation between the interplanetary magnetic field component, By, and the geopotential height anomaly above Antarctica. The correlation is most statistically significant within the troposphere. The peak in the correlation occurs at greater timelags at the tropopause (~6–8 days) and in the mid-troposphere (~4 days), than in the lower troposphere (~1 day). This supports a mechanism involving the action of the global atmospheric electric circuit, modified by variations in the solar wind, on lower tropospheric clouds. The increase in timelag with increasing altitude is consistent with the upward propagation by conventional atmospheric processes of the solar-wind-induced variability in the lower troposphere. This is in contrast to the downward propagation of atmospheric effects to the lower troposphere from the stratosphere due to solar-variability-driven mechanisms involving ultra-violet radiation or energetic particle precipitation.

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